My U.S. Pat. No. 4,874,066, issued Oct. 17, 1989 relates to a shock absorber which provides variable damping when needed, independent of the positioning of the shock absorber piston in its associated cylinder.
More particularly, the piston disclosed in such patent defines first and second chambers in the cylinder and a primary passageway permitting the flow of fluid from the first chamber into the second chamber as fluid is pressurized in the first chamber by movement of the piston. The piston includes relatively movable first and second piston elements defining a variable-sized, fluid-filled space in communication with a chamber through a vent.
The second piston element is displaceable relative to the first piston element when pressure of the fluid in the first chamber increases to reduce the size of the space and force fluid from the space through the vent into the second chamber. The piston elements include means cooperable to change the effective size of the primary passageway substantially simultaneously with, and as a function of, reduction of the size of the space.
In the arrangement just described, the vent size remains the same. Thus, the rate of flow of fluid from the space to the second chamber is solely a function of the pressure of fluid in the space.